Biology & Fluorescence
Summer time in the Phoenix area holds many surprises. Mid to high 100’s in the afternoon are common, though sometimes we can exceed 118F in June. One evening, I went out with my UV flashlight and camera and snapped this photo of a common problem we have here: Scorpions. Scorpions play an extremely important role in the ecology of the Sonoran Desert, but are only a problem when they get inside your home. The scorpions in the Phoenix area are not deadly, but the sting can be extremely painful because of the neurotoxins they inject. Scorpions were here long before the first Native Americans arrived about 1,500 years ago. I don’t see scorpions as a “problem” except when they are hiking across my living room floor, which has happened many times.
I often find one in a typical June or July evening and decided to add this photograph to show one of Nature’s magnificent displays of fluorescence.
Fluorescence is the visible emission of light that is stimulated by shorter wavelength Ultraviolet (UV) light that we can’t see. The flashlight I used to make the photo is an inexpensive hardware brand with UV LEDs that have a peak wavelength of 390-400nm, (nm, or nanometer is 10-9 meters). 390-400nm is just outside the photopic curve of the human eye, and the light that fluoresces is about 550nm, which is right next to the peak of the human eye sensitivity. (See my blog Why is the Sky Blue? for the photopic curve of the human eye.)
Some jellyfish use fluorescence in their tentacles, such as the Olindias formosa, to attract prey. Fluorescence should not be confused with bioluminescence, which is light emission by a chemical reaction. Many common household items fluoresce such as highlighter pens, tooth whiteners and bleach, (try your white socks if you have a UV light or blacklight). But it is nature that gives us such spectacular displays of fluorescence.